1 2config PRINTK_TIME 3 bool "Show timing information on printks" 4 depends on PRINTK 5 help 6 Selecting this option causes timing information to be 7 included in printk output. This allows you to measure 8 the interval between kernel operations, including bootup 9 operations. This is useful for identifying long delays 10 in kernel startup. 11 12config ENABLE_WARN_DEPRECATED 13 bool "Enable __deprecated logic" 14 default y 15 help 16 Enable the __deprecated logic in the kernel build. 17 Disable this to suppress the "warning: 'foo' is deprecated 18 (declared at kernel/power/somefile.c:1234)" messages. 19 20config ENABLE_MUST_CHECK 21 bool "Enable __must_check logic" 22 default y 23 help 24 Enable the __must_check logic in the kernel build. Disable this to 25 suppress the "warning: ignoring return value of 'foo', declared with 26 attribute warn_unused_result" messages. 27 28config FRAME_WARN 29 int "Warn for stack frames larger than (needs gcc 4.4)" 30 range 0 8192 31 default 1024 if !64BIT 32 default 2048 if 64BIT 33 help 34 Tell gcc to warn at build time for stack frames larger than this. 35 Setting this too low will cause a lot of warnings. 36 Setting it to 0 disables the warning. 37 Requires gcc 4.4 38 39config MAGIC_SYSRQ 40 bool "Magic SysRq key" 41 depends on !UML 42 help 43 If you say Y here, you will have some control over the system even 44 if the system crashes for example during kernel debugging (e.g., you 45 will be able to flush the buffer cache to disk, reboot the system 46 immediately or dump some status information). This is accomplished 47 by pressing various keys while holding SysRq (Alt+PrintScreen). It 48 also works on a serial console (on PC hardware at least), if you 49 send a BREAK and then within 5 seconds a command keypress. The 50 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 51 unless you really know what this hack does. 52 53config STRIP_ASM_SYMS 54 bool "Strip assembler-generated symbols during link" 55 default n 56 help 57 Strip internal assembler-generated symbols during a link (symbols 58 that look like '.Lxxx') so they don't pollute the output of 59 get_wchan() and suchlike. 60 61config UNUSED_SYMBOLS 62 bool "Enable unused/obsolete exported symbols" 63 default y if X86 64 help 65 Unused but exported symbols make the kernel needlessly bigger. For 66 that reason most of these unused exports will soon be removed. This 67 option is provided temporarily to provide a transition period in case 68 some external kernel module needs one of these symbols anyway. If you 69 encounter such a case in your module, consider if you are actually 70 using the right API. (rationale: since nobody in the kernel is using 71 this in a module, there is a pretty good chance it's actually the 72 wrong interface to use). If you really need the symbol, please send a 73 mail to the linux kernel mailing list mentioning the symbol and why 74 you really need it, and what the merge plan to the mainline kernel for 75 your module is. 76 77config DEBUG_FS 78 bool "Debug Filesystem" 79 help 80 debugfs is a virtual file system that kernel developers use to put 81 debugging files into. Enable this option to be able to read and 82 write to these files. 83 84 For detailed documentation on the debugfs API, see 85 Documentation/DocBook/filesystems. 86 87 If unsure, say N. 88 89config HEADERS_CHECK 90 bool "Run 'make headers_check' when building vmlinux" 91 depends on !UML 92 help 93 This option will extract the user-visible kernel headers whenever 94 building the kernel, and will run basic sanity checks on them to 95 ensure that exported files do not attempt to include files which 96 were not exported, etc. 97 98 If you're making modifications to header files which are 99 relevant for userspace, say 'Y', and check the headers 100 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 101 your build tree), to make sure they're suitable. 102 103config DEBUG_SECTION_MISMATCH 104 bool "Enable full Section mismatch analysis" 105 depends on UNDEFINED || (BLACKFIN) 106 default y 107 # This option is on purpose disabled for now. 108 # It will be enabled when we are down to a reasonable number 109 # of section mismatch warnings (< 10 for an allyesconfig build) 110 help 111 The section mismatch analysis checks if there are illegal 112 references from one section to another section. 113 Linux will during link or during runtime drop some sections 114 and any use of code/data previously in these sections will 115 most likely result in an oops. 116 In the code functions and variables are annotated with 117 __init, __devinit etc. (see full list in include/linux/init.h) 118 which results in the code/data being placed in specific sections. 119 The section mismatch analysis is always done after a full 120 kernel build but enabling this option will in addition 121 do the following: 122 - Add the option -fno-inline-functions-called-once to gcc 123 When inlining a function annotated __init in a non-init 124 function we would lose the section information and thus 125 the analysis would not catch the illegal reference. 126 This option tells gcc to inline less but will also 127 result in a larger kernel. 128 - Run the section mismatch analysis for each module/built-in.o 129 When we run the section mismatch analysis on vmlinux.o we 130 lose valueble information about where the mismatch was 131 introduced. 132 Running the analysis for each module/built-in.o file 133 will tell where the mismatch happens much closer to the 134 source. The drawback is that we will report the same 135 mismatch at least twice. 136 - Enable verbose reporting from modpost to help solving 137 the section mismatches reported. 138 139config DEBUG_KERNEL 140 bool "Kernel debugging" 141 help 142 Say Y here if you are developing drivers or trying to debug and 143 identify kernel problems. 144 145config DEBUG_SHIRQ 146 bool "Debug shared IRQ handlers" 147 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 148 help 149 Enable this to generate a spurious interrupt as soon as a shared 150 interrupt handler is registered, and just before one is deregistered. 151 Drivers ought to be able to handle interrupts coming in at those 152 points; some don't and need to be caught. 153 154config LOCKUP_DETECTOR 155 bool "Detect Hard and Soft Lockups" 156 depends on DEBUG_KERNEL && !S390 157 help 158 Say Y here to enable the kernel to act as a watchdog to detect 159 hard and soft lockups. 160 161 Softlockups are bugs that cause the kernel to loop in kernel 162 mode for more than 60 seconds, without giving other tasks a 163 chance to run. The current stack trace is displayed upon 164 detection and the system will stay locked up. 165 166 Hardlockups are bugs that cause the CPU to loop in kernel mode 167 for more than 60 seconds, without letting other interrupts have a 168 chance to run. The current stack trace is displayed upon detection 169 and the system will stay locked up. 170 171 The overhead should be minimal. A periodic hrtimer runs to 172 generate interrupts and kick the watchdog task every 10-12 seconds. 173 An NMI is generated every 60 seconds or so to check for hardlockups. 174 175config HARDLOCKUP_DETECTOR 176 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI 177 178config BOOTPARAM_SOFTLOCKUP_PANIC 179 bool "Panic (Reboot) On Soft Lockups" 180 depends on LOCKUP_DETECTOR 181 help 182 Say Y here to enable the kernel to panic on "soft lockups", 183 which are bugs that cause the kernel to loop in kernel 184 mode for more than 60 seconds, without giving other tasks a 185 chance to run. 186 187 The panic can be used in combination with panic_timeout, 188 to cause the system to reboot automatically after a 189 lockup has been detected. This feature is useful for 190 high-availability systems that have uptime guarantees and 191 where a lockup must be resolved ASAP. 192 193 Say N if unsure. 194 195config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 196 int 197 depends on LOCKUP_DETECTOR 198 range 0 1 199 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 200 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 201 202config DETECT_HUNG_TASK 203 bool "Detect Hung Tasks" 204 depends on DEBUG_KERNEL 205 default DETECT_SOFTLOCKUP 206 help 207 Say Y here to enable the kernel to detect "hung tasks", 208 which are bugs that cause the task to be stuck in 209 uninterruptible "D" state indefinitiley. 210 211 When a hung task is detected, the kernel will print the 212 current stack trace (which you should report), but the 213 task will stay in uninterruptible state. If lockdep is 214 enabled then all held locks will also be reported. This 215 feature has negligible overhead. 216 217config BOOTPARAM_HUNG_TASK_PANIC 218 bool "Panic (Reboot) On Hung Tasks" 219 depends on DETECT_HUNG_TASK 220 help 221 Say Y here to enable the kernel to panic on "hung tasks", 222 which are bugs that cause the kernel to leave a task stuck 223 in uninterruptible "D" state. 224 225 The panic can be used in combination with panic_timeout, 226 to cause the system to reboot automatically after a 227 hung task has been detected. This feature is useful for 228 high-availability systems that have uptime guarantees and 229 where a hung tasks must be resolved ASAP. 230 231 Say N if unsure. 232 233config BOOTPARAM_HUNG_TASK_PANIC_VALUE 234 int 235 depends on DETECT_HUNG_TASK 236 range 0 1 237 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 238 default 1 if BOOTPARAM_HUNG_TASK_PANIC 239 240config SCHED_DEBUG 241 bool "Collect scheduler debugging info" 242 depends on DEBUG_KERNEL && PROC_FS 243 default y 244 help 245 If you say Y here, the /proc/sched_debug file will be provided 246 that can help debug the scheduler. The runtime overhead of this 247 option is minimal. 248 249config SCHEDSTATS 250 bool "Collect scheduler statistics" 251 depends on DEBUG_KERNEL && PROC_FS 252 help 253 If you say Y here, additional code will be inserted into the 254 scheduler and related routines to collect statistics about 255 scheduler behavior and provide them in /proc/schedstat. These 256 stats may be useful for both tuning and debugging the scheduler 257 If you aren't debugging the scheduler or trying to tune a specific 258 application, you can say N to avoid the very slight overhead 259 this adds. 260 261config TIMER_STATS 262 bool "Collect kernel timers statistics" 263 depends on DEBUG_KERNEL && PROC_FS 264 help 265 If you say Y here, additional code will be inserted into the 266 timer routines to collect statistics about kernel timers being 267 reprogrammed. The statistics can be read from /proc/timer_stats. 268 The statistics collection is started by writing 1 to /proc/timer_stats, 269 writing 0 stops it. This feature is useful to collect information 270 about timer usage patterns in kernel and userspace. This feature 271 is lightweight if enabled in the kernel config but not activated 272 (it defaults to deactivated on bootup and will only be activated 273 if some application like powertop activates it explicitly). 274 275config DEBUG_OBJECTS 276 bool "Debug object operations" 277 depends on DEBUG_KERNEL 278 help 279 If you say Y here, additional code will be inserted into the 280 kernel to track the life time of various objects and validate 281 the operations on those objects. 282 283config DEBUG_OBJECTS_SELFTEST 284 bool "Debug objects selftest" 285 depends on DEBUG_OBJECTS 286 help 287 This enables the selftest of the object debug code. 288 289config DEBUG_OBJECTS_FREE 290 bool "Debug objects in freed memory" 291 depends on DEBUG_OBJECTS 292 help 293 This enables checks whether a k/v free operation frees an area 294 which contains an object which has not been deactivated 295 properly. This can make kmalloc/kfree-intensive workloads 296 much slower. 297 298config DEBUG_OBJECTS_TIMERS 299 bool "Debug timer objects" 300 depends on DEBUG_OBJECTS 301 help 302 If you say Y here, additional code will be inserted into the 303 timer routines to track the life time of timer objects and 304 validate the timer operations. 305 306config DEBUG_OBJECTS_WORK 307 bool "Debug work objects" 308 depends on DEBUG_OBJECTS 309 help 310 If you say Y here, additional code will be inserted into the 311 work queue routines to track the life time of work objects and 312 validate the work operations. 313 314config DEBUG_OBJECTS_RCU_HEAD 315 bool "Debug RCU callbacks objects" 316 depends on DEBUG_OBJECTS && PREEMPT 317 help 318 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 319 320config DEBUG_OBJECTS_PERCPU_COUNTER 321 bool "Debug percpu counter objects" 322 depends on DEBUG_OBJECTS 323 help 324 If you say Y here, additional code will be inserted into the 325 percpu counter routines to track the life time of percpu counter 326 objects and validate the percpu counter operations. 327 328config DEBUG_OBJECTS_ENABLE_DEFAULT 329 int "debug_objects bootup default value (0-1)" 330 range 0 1 331 default "1" 332 depends on DEBUG_OBJECTS 333 help 334 Debug objects boot parameter default value 335 336config DEBUG_SLAB 337 bool "Debug slab memory allocations" 338 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 339 help 340 Say Y here to have the kernel do limited verification on memory 341 allocation as well as poisoning memory on free to catch use of freed 342 memory. This can make kmalloc/kfree-intensive workloads much slower. 343 344config DEBUG_SLAB_LEAK 345 bool "Memory leak debugging" 346 depends on DEBUG_SLAB 347 348config SLUB_DEBUG_ON 349 bool "SLUB debugging on by default" 350 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 351 default n 352 help 353 Boot with debugging on by default. SLUB boots by default with 354 the runtime debug capabilities switched off. Enabling this is 355 equivalent to specifying the "slub_debug" parameter on boot. 356 There is no support for more fine grained debug control like 357 possible with slub_debug=xxx. SLUB debugging may be switched 358 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 359 "slub_debug=-". 360 361config SLUB_STATS 362 default n 363 bool "Enable SLUB performance statistics" 364 depends on SLUB && SYSFS 365 help 366 SLUB statistics are useful to debug SLUBs allocation behavior in 367 order find ways to optimize the allocator. This should never be 368 enabled for production use since keeping statistics slows down 369 the allocator by a few percentage points. The slabinfo command 370 supports the determination of the most active slabs to figure 371 out which slabs are relevant to a particular load. 372 Try running: slabinfo -DA 373 374config DEBUG_KMEMLEAK 375 bool "Kernel memory leak detector" 376 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \ 377 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE) 378 379 select DEBUG_FS if SYSFS 380 select STACKTRACE if STACKTRACE_SUPPORT 381 select KALLSYMS 382 select CRC32 383 help 384 Say Y here if you want to enable the memory leak 385 detector. The memory allocation/freeing is traced in a way 386 similar to the Boehm's conservative garbage collector, the 387 difference being that the orphan objects are not freed but 388 only shown in /sys/kernel/debug/kmemleak. Enabling this 389 feature will introduce an overhead to memory 390 allocations. See Documentation/kmemleak.txt for more 391 details. 392 393 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 394 of finding leaks due to the slab objects poisoning. 395 396 In order to access the kmemleak file, debugfs needs to be 397 mounted (usually at /sys/kernel/debug). 398 399config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 400 int "Maximum kmemleak early log entries" 401 depends on DEBUG_KMEMLEAK 402 range 200 40000 403 default 400 404 help 405 Kmemleak must track all the memory allocations to avoid 406 reporting false positives. Since memory may be allocated or 407 freed before kmemleak is initialised, an early log buffer is 408 used to store these actions. If kmemleak reports "early log 409 buffer exceeded", please increase this value. 410 411config DEBUG_KMEMLEAK_TEST 412 tristate "Simple test for the kernel memory leak detector" 413 depends on DEBUG_KMEMLEAK 414 help 415 Say Y or M here to build a test for the kernel memory leak 416 detector. This option enables a module that explicitly leaks 417 memory. 418 419 If unsure, say N. 420 421config DEBUG_KMEMLEAK_DEFAULT_OFF 422 bool "Default kmemleak to off" 423 depends on DEBUG_KMEMLEAK 424 help 425 Say Y here to disable kmemleak by default. It can then be enabled 426 on the command line via kmemleak=on. 427 428config DEBUG_PREEMPT 429 bool "Debug preemptible kernel" 430 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 431 default y 432 help 433 If you say Y here then the kernel will use a debug variant of the 434 commonly used smp_processor_id() function and will print warnings 435 if kernel code uses it in a preemption-unsafe way. Also, the kernel 436 will detect preemption count underflows. 437 438config DEBUG_RT_MUTEXES 439 bool "RT Mutex debugging, deadlock detection" 440 depends on DEBUG_KERNEL && RT_MUTEXES 441 help 442 This allows rt mutex semantics violations and rt mutex related 443 deadlocks (lockups) to be detected and reported automatically. 444 445config DEBUG_PI_LIST 446 bool 447 default y 448 depends on DEBUG_RT_MUTEXES 449 450config RT_MUTEX_TESTER 451 bool "Built-in scriptable tester for rt-mutexes" 452 depends on DEBUG_KERNEL && RT_MUTEXES 453 help 454 This option enables a rt-mutex tester. 455 456config DEBUG_SPINLOCK 457 bool "Spinlock and rw-lock debugging: basic checks" 458 depends on DEBUG_KERNEL 459 help 460 Say Y here and build SMP to catch missing spinlock initialization 461 and certain other kinds of spinlock errors commonly made. This is 462 best used in conjunction with the NMI watchdog so that spinlock 463 deadlocks are also debuggable. 464 465config DEBUG_MUTEXES 466 bool "Mutex debugging: basic checks" 467 depends on DEBUG_KERNEL 468 help 469 This feature allows mutex semantics violations to be detected and 470 reported. 471 472config BKL 473 bool "Big Kernel Lock" if (SMP || PREEMPT) 474 default y 475 help 476 This is the traditional lock that is used in old code instead 477 of proper locking. All drivers that use the BKL should depend 478 on this symbol. 479 Say Y here unless you are working on removing the BKL. 480 481config DEBUG_LOCK_ALLOC 482 bool "Lock debugging: detect incorrect freeing of live locks" 483 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 484 select DEBUG_SPINLOCK 485 select DEBUG_MUTEXES 486 select LOCKDEP 487 help 488 This feature will check whether any held lock (spinlock, rwlock, 489 mutex or rwsem) is incorrectly freed by the kernel, via any of the 490 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 491 vfree(), etc.), whether a live lock is incorrectly reinitialized via 492 spin_lock_init()/mutex_init()/etc., or whether there is any lock 493 held during task exit. 494 495config PROVE_LOCKING 496 bool "Lock debugging: prove locking correctness" 497 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 498 select LOCKDEP 499 select DEBUG_SPINLOCK 500 select DEBUG_MUTEXES 501 select DEBUG_LOCK_ALLOC 502 select TRACE_IRQFLAGS 503 default n 504 help 505 This feature enables the kernel to prove that all locking 506 that occurs in the kernel runtime is mathematically 507 correct: that under no circumstance could an arbitrary (and 508 not yet triggered) combination of observed locking 509 sequences (on an arbitrary number of CPUs, running an 510 arbitrary number of tasks and interrupt contexts) cause a 511 deadlock. 512 513 In short, this feature enables the kernel to report locking 514 related deadlocks before they actually occur. 515 516 The proof does not depend on how hard and complex a 517 deadlock scenario would be to trigger: how many 518 participant CPUs, tasks and irq-contexts would be needed 519 for it to trigger. The proof also does not depend on 520 timing: if a race and a resulting deadlock is possible 521 theoretically (no matter how unlikely the race scenario 522 is), it will be proven so and will immediately be 523 reported by the kernel (once the event is observed that 524 makes the deadlock theoretically possible). 525 526 If a deadlock is impossible (i.e. the locking rules, as 527 observed by the kernel, are mathematically correct), the 528 kernel reports nothing. 529 530 NOTE: this feature can also be enabled for rwlocks, mutexes 531 and rwsems - in which case all dependencies between these 532 different locking variants are observed and mapped too, and 533 the proof of observed correctness is also maintained for an 534 arbitrary combination of these separate locking variants. 535 536 For more details, see Documentation/lockdep-design.txt. 537 538config PROVE_RCU 539 bool "RCU debugging: prove RCU correctness" 540 depends on PROVE_LOCKING 541 default n 542 help 543 This feature enables lockdep extensions that check for correct 544 use of RCU APIs. This is currently under development. Say Y 545 if you want to debug RCU usage or help work on the PROVE_RCU 546 feature. 547 548 Say N if you are unsure. 549 550config PROVE_RCU_REPEATEDLY 551 bool "RCU debugging: don't disable PROVE_RCU on first splat" 552 depends on PROVE_RCU 553 default n 554 help 555 By itself, PROVE_RCU will disable checking upon issuing the 556 first warning (or "splat"). This feature prevents such 557 disabling, allowing multiple RCU-lockdep warnings to be printed 558 on a single reboot. 559 560 Say Y to allow multiple RCU-lockdep warnings per boot. 561 562 Say N if you are unsure. 563 564config SPARSE_RCU_POINTER 565 bool "RCU debugging: sparse-based checks for pointer usage" 566 default n 567 help 568 This feature enables the __rcu sparse annotation for 569 RCU-protected pointers. This annotation will cause sparse 570 to flag any non-RCU used of annotated pointers. This can be 571 helpful when debugging RCU usage. Please note that this feature 572 is not intended to enforce code cleanliness; it is instead merely 573 a debugging aid. 574 575 Say Y to make sparse flag questionable use of RCU-protected pointers 576 577 Say N if you are unsure. 578 579config LOCKDEP 580 bool 581 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 582 select STACKTRACE 583 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 584 select KALLSYMS 585 select KALLSYMS_ALL 586 587config LOCK_STAT 588 bool "Lock usage statistics" 589 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 590 select LOCKDEP 591 select DEBUG_SPINLOCK 592 select DEBUG_MUTEXES 593 select DEBUG_LOCK_ALLOC 594 default n 595 help 596 This feature enables tracking lock contention points 597 598 For more details, see Documentation/lockstat.txt 599 600 This also enables lock events required by "perf lock", 601 subcommand of perf. 602 If you want to use "perf lock", you also need to turn on 603 CONFIG_EVENT_TRACING. 604 605 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 606 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 607 608config DEBUG_LOCKDEP 609 bool "Lock dependency engine debugging" 610 depends on DEBUG_KERNEL && LOCKDEP 611 help 612 If you say Y here, the lock dependency engine will do 613 additional runtime checks to debug itself, at the price 614 of more runtime overhead. 615 616config TRACE_IRQFLAGS 617 bool 618 help 619 Enables hooks to interrupt enabling and disabling for 620 either tracing or lock debugging. 621 622config DEBUG_SPINLOCK_SLEEP 623 bool "Spinlock debugging: sleep-inside-spinlock checking" 624 depends on DEBUG_KERNEL 625 help 626 If you say Y here, various routines which may sleep will become very 627 noisy if they are called with a spinlock held. 628 629config DEBUG_LOCKING_API_SELFTESTS 630 bool "Locking API boot-time self-tests" 631 depends on DEBUG_KERNEL 632 help 633 Say Y here if you want the kernel to run a short self-test during 634 bootup. The self-test checks whether common types of locking bugs 635 are detected by debugging mechanisms or not. (if you disable 636 lock debugging then those bugs wont be detected of course.) 637 The following locking APIs are covered: spinlocks, rwlocks, 638 mutexes and rwsems. 639 640config STACKTRACE 641 bool 642 depends on STACKTRACE_SUPPORT 643 644config DEBUG_KOBJECT 645 bool "kobject debugging" 646 depends on DEBUG_KERNEL 647 help 648 If you say Y here, some extra kobject debugging messages will be sent 649 to the syslog. 650 651config DEBUG_HIGHMEM 652 bool "Highmem debugging" 653 depends on DEBUG_KERNEL && HIGHMEM 654 help 655 This options enables addition error checking for high memory systems. 656 Disable for production systems. 657 658config DEBUG_BUGVERBOSE 659 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 660 depends on BUG 661 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 662 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 663 default y 664 help 665 Say Y here to make BUG() panics output the file name and line number 666 of the BUG call as well as the EIP and oops trace. This aids 667 debugging but costs about 70-100K of memory. 668 669config DEBUG_INFO 670 bool "Compile the kernel with debug info" 671 depends on DEBUG_KERNEL 672 help 673 If you say Y here the resulting kernel image will include 674 debugging info resulting in a larger kernel image. 675 This adds debug symbols to the kernel and modules (gcc -g), and 676 is needed if you intend to use kernel crashdump or binary object 677 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 678 Say Y here only if you plan to debug the kernel. 679 680 If unsure, say N. 681 682config DEBUG_INFO_REDUCED 683 bool "Reduce debugging information" 684 depends on DEBUG_INFO 685 help 686 If you say Y here gcc is instructed to generate less debugging 687 information for structure types. This means that tools that 688 need full debugging information (like kgdb or systemtap) won't 689 be happy. But if you merely need debugging information to 690 resolve line numbers there is no loss. Advantage is that 691 build directory object sizes shrink dramatically over a full 692 DEBUG_INFO build and compile times are reduced too. 693 Only works with newer gcc versions. 694 695config DEBUG_VM 696 bool "Debug VM" 697 depends on DEBUG_KERNEL 698 help 699 Enable this to turn on extended checks in the virtual-memory system 700 that may impact performance. 701 702 If unsure, say N. 703 704config DEBUG_VIRTUAL 705 bool "Debug VM translations" 706 depends on DEBUG_KERNEL && X86 707 help 708 Enable some costly sanity checks in virtual to page code. This can 709 catch mistakes with virt_to_page() and friends. 710 711 If unsure, say N. 712 713config DEBUG_NOMMU_REGIONS 714 bool "Debug the global anon/private NOMMU mapping region tree" 715 depends on DEBUG_KERNEL && !MMU 716 help 717 This option causes the global tree of anonymous and private mapping 718 regions to be regularly checked for invalid topology. 719 720config DEBUG_WRITECOUNT 721 bool "Debug filesystem writers count" 722 depends on DEBUG_KERNEL 723 help 724 Enable this to catch wrong use of the writers count in struct 725 vfsmount. This will increase the size of each file struct by 726 32 bits. 727 728 If unsure, say N. 729 730config DEBUG_MEMORY_INIT 731 bool "Debug memory initialisation" if EMBEDDED 732 default !EMBEDDED 733 help 734 Enable this for additional checks during memory initialisation. 735 The sanity checks verify aspects of the VM such as the memory model 736 and other information provided by the architecture. Verbose 737 information will be printed at KERN_DEBUG loglevel depending 738 on the mminit_loglevel= command-line option. 739 740 If unsure, say Y 741 742config DEBUG_LIST 743 bool "Debug linked list manipulation" 744 depends on DEBUG_KERNEL 745 help 746 Enable this to turn on extended checks in the linked-list 747 walking routines. 748 749 If unsure, say N. 750 751config TEST_LIST_SORT 752 bool "Linked list sorting test" 753 depends on DEBUG_KERNEL 754 help 755 Enable this to turn on 'list_sort()' function test. This test is 756 executed only once during system boot, so affects only boot time. 757 758 If unsure, say N. 759 760config DEBUG_SG 761 bool "Debug SG table operations" 762 depends on DEBUG_KERNEL 763 help 764 Enable this to turn on checks on scatter-gather tables. This can 765 help find problems with drivers that do not properly initialize 766 their sg tables. 767 768 If unsure, say N. 769 770config DEBUG_NOTIFIERS 771 bool "Debug notifier call chains" 772 depends on DEBUG_KERNEL 773 help 774 Enable this to turn on sanity checking for notifier call chains. 775 This is most useful for kernel developers to make sure that 776 modules properly unregister themselves from notifier chains. 777 This is a relatively cheap check but if you care about maximum 778 performance, say N. 779 780config DEBUG_CREDENTIALS 781 bool "Debug credential management" 782 depends on DEBUG_KERNEL 783 help 784 Enable this to turn on some debug checking for credential 785 management. The additional code keeps track of the number of 786 pointers from task_structs to any given cred struct, and checks to 787 see that this number never exceeds the usage count of the cred 788 struct. 789 790 Furthermore, if SELinux is enabled, this also checks that the 791 security pointer in the cred struct is never seen to be invalid. 792 793 If unsure, say N. 794 795# 796# Select this config option from the architecture Kconfig, if it 797# it is preferred to always offer frame pointers as a config 798# option on the architecture (regardless of KERNEL_DEBUG): 799# 800config ARCH_WANT_FRAME_POINTERS 801 bool 802 help 803 804config FRAME_POINTER 805 bool "Compile the kernel with frame pointers" 806 depends on DEBUG_KERNEL && \ 807 (CRIS || M68K || M68KNOMMU || FRV || UML || \ 808 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 809 ARCH_WANT_FRAME_POINTERS 810 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 811 help 812 If you say Y here the resulting kernel image will be slightly 813 larger and slower, but it gives very useful debugging information 814 in case of kernel bugs. (precise oopses/stacktraces/warnings) 815 816config BOOT_PRINTK_DELAY 817 bool "Delay each boot printk message by N milliseconds" 818 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 819 help 820 This build option allows you to read kernel boot messages 821 by inserting a short delay after each one. The delay is 822 specified in milliseconds on the kernel command line, 823 using "boot_delay=N". 824 825 It is likely that you would also need to use "lpj=M" to preset 826 the "loops per jiffie" value. 827 See a previous boot log for the "lpj" value to use for your 828 system, and then set "lpj=M" before setting "boot_delay=N". 829 NOTE: Using this option may adversely affect SMP systems. 830 I.e., processors other than the first one may not boot up. 831 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 832 what it believes to be lockup conditions. 833 834config RCU_TORTURE_TEST 835 tristate "torture tests for RCU" 836 depends on DEBUG_KERNEL 837 default n 838 help 839 This option provides a kernel module that runs torture tests 840 on the RCU infrastructure. The kernel module may be built 841 after the fact on the running kernel to be tested, if desired. 842 843 Say Y here if you want RCU torture tests to be built into 844 the kernel. 845 Say M if you want the RCU torture tests to build as a module. 846 Say N if you are unsure. 847 848config RCU_TORTURE_TEST_RUNNABLE 849 bool "torture tests for RCU runnable by default" 850 depends on RCU_TORTURE_TEST = y 851 default n 852 help 853 This option provides a way to build the RCU torture tests 854 directly into the kernel without them starting up at boot 855 time. You can use /proc/sys/kernel/rcutorture_runnable 856 to manually override this setting. This /proc file is 857 available only when the RCU torture tests have been built 858 into the kernel. 859 860 Say Y here if you want the RCU torture tests to start during 861 boot (you probably don't). 862 Say N here if you want the RCU torture tests to start only 863 after being manually enabled via /proc. 864 865config RCU_CPU_STALL_DETECTOR 866 bool "Check for stalled CPUs delaying RCU grace periods" 867 depends on TREE_RCU || TREE_PREEMPT_RCU 868 default y 869 help 870 This option causes RCU to printk information on which 871 CPUs are delaying the current grace period, but only when 872 the grace period extends for excessive time periods. 873 874 Say N if you want to disable such checks. 875 876 Say Y if you are unsure. 877 878config RCU_CPU_STALL_TIMEOUT 879 int "RCU CPU stall timeout in seconds" 880 depends on RCU_CPU_STALL_DETECTOR 881 range 3 300 882 default 60 883 help 884 If a given RCU grace period extends more than the specified 885 number of seconds, a CPU stall warning is printed. If the 886 RCU grace period persists, additional CPU stall warnings are 887 printed at more widely spaced intervals. 888 889config RCU_CPU_STALL_DETECTOR_RUNNABLE 890 bool "RCU CPU stall checking starts automatically at boot" 891 depends on RCU_CPU_STALL_DETECTOR 892 default y 893 help 894 If set, start checking for RCU CPU stalls immediately on 895 boot. Otherwise, RCU CPU stall checking must be manually 896 enabled. 897 898 Say Y if you are unsure. 899 900 Say N if you wish to suppress RCU CPU stall checking during boot. 901 902config RCU_CPU_STALL_VERBOSE 903 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 904 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU 905 default y 906 help 907 This option causes RCU to printk detailed per-task information 908 for any tasks that are stalling the current RCU grace period. 909 910 Say N if you are unsure. 911 912 Say Y if you want to enable such checks. 913 914config KPROBES_SANITY_TEST 915 bool "Kprobes sanity tests" 916 depends on DEBUG_KERNEL 917 depends on KPROBES 918 default n 919 help 920 This option provides for testing basic kprobes functionality on 921 boot. A sample kprobe, jprobe and kretprobe are inserted and 922 verified for functionality. 923 924 Say N if you are unsure. 925 926config BACKTRACE_SELF_TEST 927 tristate "Self test for the backtrace code" 928 depends on DEBUG_KERNEL 929 default n 930 help 931 This option provides a kernel module that can be used to test 932 the kernel stack backtrace code. This option is not useful 933 for distributions or general kernels, but only for kernel 934 developers working on architecture code. 935 936 Note that if you want to also test saved backtraces, you will 937 have to enable STACKTRACE as well. 938 939 Say N if you are unsure. 940 941config DEBUG_BLOCK_EXT_DEVT 942 bool "Force extended block device numbers and spread them" 943 depends on DEBUG_KERNEL 944 depends on BLOCK 945 default n 946 help 947 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 948 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 949 YOU ARE DOING. Distros, please enable this and fix whatever 950 is broken. 951 952 Conventionally, block device numbers are allocated from 953 predetermined contiguous area. However, extended block area 954 may introduce non-contiguous block device numbers. This 955 option forces most block device numbers to be allocated from 956 the extended space and spreads them to discover kernel or 957 userland code paths which assume predetermined contiguous 958 device number allocation. 959 960 Note that turning on this debug option shuffles all the 961 device numbers for all IDE and SCSI devices including libata 962 ones, so root partition specified using device number 963 directly (via rdev or root=MAJ:MIN) won't work anymore. 964 Textual device names (root=/dev/sdXn) will continue to work. 965 966 Say N if you are unsure. 967 968config DEBUG_FORCE_WEAK_PER_CPU 969 bool "Force weak per-cpu definitions" 970 depends on DEBUG_KERNEL 971 help 972 s390 and alpha require percpu variables in modules to be 973 defined weak to work around addressing range issue which 974 puts the following two restrictions on percpu variable 975 definitions. 976 977 1. percpu symbols must be unique whether static or not 978 2. percpu variables can't be defined inside a function 979 980 To ensure that generic code follows the above rules, this 981 option forces all percpu variables to be defined as weak. 982 983config LKDTM 984 tristate "Linux Kernel Dump Test Tool Module" 985 depends on DEBUG_FS 986 depends on BLOCK 987 default n 988 help 989 This module enables testing of the different dumping mechanisms by 990 inducing system failures at predefined crash points. 991 If you don't need it: say N 992 Choose M here to compile this code as a module. The module will be 993 called lkdtm. 994 995 Documentation on how to use the module can be found in 996 Documentation/fault-injection/provoke-crashes.txt 997 998config CPU_NOTIFIER_ERROR_INJECT 999 tristate "CPU notifier error injection module" 1000 depends on HOTPLUG_CPU && DEBUG_KERNEL 1001 help 1002 This option provides a kernel module that can be used to test 1003 the error handling of the cpu notifiers 1004 1005 To compile this code as a module, choose M here: the module will 1006 be called cpu-notifier-error-inject. 1007 1008 If unsure, say N. 1009 1010config FAULT_INJECTION 1011 bool "Fault-injection framework" 1012 depends on DEBUG_KERNEL 1013 help 1014 Provide fault-injection framework. 1015 For more details, see Documentation/fault-injection/. 1016 1017config FAILSLAB 1018 bool "Fault-injection capability for kmalloc" 1019 depends on FAULT_INJECTION 1020 depends on SLAB || SLUB 1021 help 1022 Provide fault-injection capability for kmalloc. 1023 1024config FAIL_PAGE_ALLOC 1025 bool "Fault-injection capabilitiy for alloc_pages()" 1026 depends on FAULT_INJECTION 1027 help 1028 Provide fault-injection capability for alloc_pages(). 1029 1030config FAIL_MAKE_REQUEST 1031 bool "Fault-injection capability for disk IO" 1032 depends on FAULT_INJECTION && BLOCK 1033 help 1034 Provide fault-injection capability for disk IO. 1035 1036config FAIL_IO_TIMEOUT 1037 bool "Fault-injection capability for faking disk interrupts" 1038 depends on FAULT_INJECTION && BLOCK 1039 help 1040 Provide fault-injection capability on end IO handling. This 1041 will make the block layer "forget" an interrupt as configured, 1042 thus exercising the error handling. 1043 1044 Only works with drivers that use the generic timeout handling, 1045 for others it wont do anything. 1046 1047config FAULT_INJECTION_DEBUG_FS 1048 bool "Debugfs entries for fault-injection capabilities" 1049 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1050 help 1051 Enable configuration of fault-injection capabilities via debugfs. 1052 1053config FAULT_INJECTION_STACKTRACE_FILTER 1054 bool "stacktrace filter for fault-injection capabilities" 1055 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1056 depends on !X86_64 1057 select STACKTRACE 1058 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE 1059 help 1060 Provide stacktrace filter for fault-injection capabilities 1061 1062config LATENCYTOP 1063 bool "Latency measuring infrastructure" 1064 depends on HAVE_LATENCYTOP_SUPPORT 1065 depends on DEBUG_KERNEL 1066 depends on STACKTRACE_SUPPORT 1067 depends on PROC_FS 1068 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE 1069 select KALLSYMS 1070 select KALLSYMS_ALL 1071 select STACKTRACE 1072 select SCHEDSTATS 1073 select SCHED_DEBUG 1074 help 1075 Enable this option if you want to use the LatencyTOP tool 1076 to find out which userspace is blocking on what kernel operations. 1077 1078config SYSCTL_SYSCALL_CHECK 1079 bool "Sysctl checks" 1080 depends on SYSCTL 1081 ---help--- 1082 sys_sysctl uses binary paths that have been found challenging 1083 to properly maintain and use. This enables checks that help 1084 you to keep things correct. 1085 1086source mm/Kconfig.debug 1087source kernel/trace/Kconfig 1088 1089config PROVIDE_OHCI1394_DMA_INIT 1090 bool "Remote debugging over FireWire early on boot" 1091 depends on PCI && X86 1092 help 1093 If you want to debug problems which hang or crash the kernel early 1094 on boot and the crashing machine has a FireWire port, you can use 1095 this feature to remotely access the memory of the crashed machine 1096 over FireWire. This employs remote DMA as part of the OHCI1394 1097 specification which is now the standard for FireWire controllers. 1098 1099 With remote DMA, you can monitor the printk buffer remotely using 1100 firescope and access all memory below 4GB using fireproxy from gdb. 1101 Even controlling a kernel debugger is possible using remote DMA. 1102 1103 Usage: 1104 1105 If ohci1394_dma=early is used as boot parameter, it will initialize 1106 all OHCI1394 controllers which are found in the PCI config space. 1107 1108 As all changes to the FireWire bus such as enabling and disabling 1109 devices cause a bus reset and thereby disable remote DMA for all 1110 devices, be sure to have the cable plugged and FireWire enabled on 1111 the debugging host before booting the debug target for debugging. 1112 1113 This code (~1k) is freed after boot. By then, the firewire stack 1114 in charge of the OHCI-1394 controllers should be used instead. 1115 1116 See Documentation/debugging-via-ohci1394.txt for more information. 1117 1118config FIREWIRE_OHCI_REMOTE_DMA 1119 bool "Remote debugging over FireWire with firewire-ohci" 1120 depends on FIREWIRE_OHCI 1121 help 1122 This option lets you use the FireWire bus for remote debugging 1123 with help of the firewire-ohci driver. It enables unfiltered 1124 remote DMA in firewire-ohci. 1125 See Documentation/debugging-via-ohci1394.txt for more information. 1126 1127 If unsure, say N. 1128 1129config BUILD_DOCSRC 1130 bool "Build targets in Documentation/ tree" 1131 depends on HEADERS_CHECK 1132 help 1133 This option attempts to build objects from the source files in the 1134 kernel Documentation/ tree. 1135 1136 Say N if you are unsure. 1137 1138config DYNAMIC_DEBUG 1139 bool "Enable dynamic printk() support" 1140 default n 1141 depends on PRINTK 1142 depends on DEBUG_FS 1143 help 1144 1145 Compiles debug level messages into the kernel, which would not 1146 otherwise be available at runtime. These messages can then be 1147 enabled/disabled based on various levels of scope - per source file, 1148 function, module, format string, and line number. This mechanism 1149 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 1150 this compile option is a larger kernel text size of about 2%. 1151 1152 Usage: 1153 1154 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1155 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1156 filesystem must first be mounted before making use of this feature. 1157 We refer the control file as: <debugfs>/dynamic_debug/control. This 1158 file contains a list of the debug statements that can be enabled. The 1159 format for each line of the file is: 1160 1161 filename:lineno [module]function flags format 1162 1163 filename : source file of the debug statement 1164 lineno : line number of the debug statement 1165 module : module that contains the debug statement 1166 function : function that contains the debug statement 1167 flags : 'p' means the line is turned 'on' for printing 1168 format : the format used for the debug statement 1169 1170 From a live system: 1171 1172 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1173 # filename:lineno [module]function flags format 1174 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1175 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1176 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1177 1178 Example usage: 1179 1180 // enable the message at line 1603 of file svcsock.c 1181 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1182 <debugfs>/dynamic_debug/control 1183 1184 // enable all the messages in file svcsock.c 1185 nullarbor:~ # echo -n 'file svcsock.c +p' > 1186 <debugfs>/dynamic_debug/control 1187 1188 // enable all the messages in the NFS server module 1189 nullarbor:~ # echo -n 'module nfsd +p' > 1190 <debugfs>/dynamic_debug/control 1191 1192 // enable all 12 messages in the function svc_process() 1193 nullarbor:~ # echo -n 'func svc_process +p' > 1194 <debugfs>/dynamic_debug/control 1195 1196 // disable all 12 messages in the function svc_process() 1197 nullarbor:~ # echo -n 'func svc_process -p' > 1198 <debugfs>/dynamic_debug/control 1199 1200 See Documentation/dynamic-debug-howto.txt for additional information. 1201 1202config DMA_API_DEBUG 1203 bool "Enable debugging of DMA-API usage" 1204 depends on HAVE_DMA_API_DEBUG 1205 help 1206 Enable this option to debug the use of the DMA API by device drivers. 1207 With this option you will be able to detect common bugs in device 1208 drivers like double-freeing of DMA mappings or freeing mappings that 1209 were never allocated. 1210 This option causes a performance degredation. Use only if you want 1211 to debug device drivers. If unsure, say N. 1212 1213config ATOMIC64_SELFTEST 1214 bool "Perform an atomic64_t self-test at boot" 1215 help 1216 Enable this option to test the atomic64_t functions at boot. 1217 1218 If unsure, say N. 1219 1220config ASYNC_RAID6_TEST 1221 tristate "Self test for hardware accelerated raid6 recovery" 1222 depends on ASYNC_RAID6_RECOV 1223 select ASYNC_MEMCPY 1224 ---help--- 1225 This is a one-shot self test that permutes through the 1226 recovery of all the possible two disk failure scenarios for a 1227 N-disk array. Recovery is performed with the asynchronous 1228 raid6 recovery routines, and will optionally use an offload 1229 engine if one is available. 1230 1231 If unsure, say N. 1232 1233source "samples/Kconfig" 1234 1235source "lib/Kconfig.kgdb" 1236 1237source "lib/Kconfig.kmemcheck" 1238